Many instruments today require digital signal processing ("DSP") to extract the maximum information from electronic signals. DSP often requires that the signal be sampled and stored in memory for a certain time period. The length of time in the period depends upon the algorithm used for DSP. In many cases, the signals of interest occur in short bursts and at random time intervals. This makes it impossible to predict in advance when the signal that contains pertinent information will be present or not present. Also, the processing time of the DSP algorithm can be long compared to the signal burst time. Thus, if a continuous block sampling technique is used, the efficiency of processing the available signal may be very low.
Although numerous measuring devices, such as radar and sonar among others, operate such that the basic signal generated by the transducer includes random bursts of coherent frequencies on a background of white noise, the example used herein will be that of the laser dopler velocimeter ("LDV"). As those skilled in the art will appreciate, the LDV operates to produce a signal indicative of the speed of a particle traversing the intersection of two laser beams. The produced signal has both a duration and a frequency which are of interest.
In the past, typically an analog level detector was utilized to determine when a burst was present in an LDV signal. However, such a system had the following drawbacks: the system detected amplitude rather than coherence, the system was amplitude dependent, the system had a low amplitude dynamic range and the system required a relatively high signal to noise ratio.
Therefore, there arises a need for a burst detector which is capable of triggering a block sampler to acquire a sample block of the desired signal. By doing so, the DSP algorithm efficiency improves significantly (i.e., the ratio between the time spent processing signals with pertinent information compared to time spent processing signals that contain no pertinent information). Also, there arises a need for a burst detector which prevents losing data due to the data occurring at a small percentage of the time. The present invention directly addresses and overcomes the shortcomings of the prior art.